// Copyright 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_TREES_OCCLUSION_TRACKER_H_
#define CC_TREES_OCCLUSION_TRACKER_H_
#include <vector>
#include "base/basictypes.h"
#include "cc/base/cc_export.h"
#include "cc/base/region.h"
#include "cc/layers/layer_iterator.h"
#include "ui/gfx/rect.h"
namespace cc {
class LayerImpl;
class RenderSurfaceImpl;
class Layer;
class RenderSurface;
// This class is used to track occlusion of layers while traversing them in a
// front-to-back order. As each layer is visited, one of the methods in this
// class is called to notify it about the current target surface. Then,
// occlusion in the content space of the current layer may be queried, via
// methods such as Occluded() and UnoccludedContentRect(). If the current layer
// owns a RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also
// be queried via surfaceOccluded() and surfaceUnoccludedContentRect(). Finally,
// once finished with the layer, occlusion behind the layer should be marked by
// calling MarkOccludedBehindLayer().
template <typename LayerType>
class CC_EXPORT OcclusionTracker {
public:
explicit OcclusionTracker(const gfx::Rect& screen_space_clip_rect);
~OcclusionTracker();
// Called at the beginning of each step in the LayerIterator's front-to-back
// traversal.
void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
// Called at the end of each step in the LayerIterator's front-to-back
// traversal.
void LeaveLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
// Returns true if the given rect in content space for a layer is fully
// occluded in either screen space or the layer's target surface.
// |render_target| is the contributing layer's render target, and
// |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
bool Occluded(const LayerType* render_target,
const gfx::Rect& content_rect,
const gfx::Transform& draw_transform) const;
// Gives an unoccluded sub-rect of |content_rect| in the content space of a
// layer. Used when considering occlusion for a layer that paints/draws
// something. |render_target| is the contributing layer's render target, and
// |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
gfx::Rect UnoccludedContentRect(const LayerType* render_target,
const gfx::Rect& content_rect,
const gfx::Transform& draw_transform) const;
// Gives an unoccluded sub-rect of |content_rect| in the content space of the
// render_target owned by the layer. Used when considering occlusion for a
// contributing surface that is rendering into another target.
gfx::Rect UnoccludedContributingSurfaceContentRect(
const LayerType* layer,
const gfx::Rect& content_rect,
const gfx::Transform& draw_transform) const;
// Gives the region of the screen that is not occluded by something opaque.
Region ComputeVisibleRegionInScreen() const {
DCHECK(!stack_.back().target->parent());
return SubtractRegions(screen_space_clip_rect_,
stack_.back().occlusion_from_inside_target);
}
void set_minimum_tracking_size(const gfx::Size& size) {
minimum_tracking_size_ = size;
}
// The following is used for visualization purposes.
void set_occluding_screen_space_rects_container(
std::vector<gfx::Rect>* rects) {
occluding_screen_space_rects_ = rects;
}
void set_non_occluding_screen_space_rects_container(
std::vector<gfx::Rect>* rects) {
non_occluding_screen_space_rects_ = rects;
}
protected:
struct StackObject {
StackObject() : target(0) {}
explicit StackObject(const LayerType* target) : target(target) {}
const LayerType* target;
Region occlusion_from_outside_target;
Region occlusion_from_inside_target;
};
// The stack holds occluded regions for subtrees in the
// RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
// a mask to it, but not to the parts outside the subtree.
// - The first time we see a new subtree under a target, we add that target to
// the top of the stack. This can happen as a layer representing itself, or as
// a target surface.
// - When we visit a target surface, we apply its mask to its subtree, which
// is at the top of the stack.
// - When we visit a layer representing itself, we add its occlusion to the
// current subtree, which is at the top of the stack.
// - When we visit a layer representing a contributing surface, the current
// target will never be the top of the stack since we just came from the
// contributing surface.
// We merge the occlusion at the top of the stack with the new current
// subtree. This new target is pushed onto the stack if not already there.
std::vector<StackObject> stack_;
private:
// Called when visiting a layer representing itself. If the target was not
// already current, then this indicates we have entered a new surface subtree.
void EnterRenderTarget(const LayerType* new_target);
// Called when visiting a layer representing a target surface. This indicates
// we have visited all the layers within the surface, and we may perform any
// surface-wide operations.
void FinishedRenderTarget(const LayerType* finished_target);
// Called when visiting a layer representing a contributing surface. This
// indicates that we are leaving our current surface, and entering the new
// one. We then perform any operations required for merging results from the
// child subtree into its parent.
void LeaveToRenderTarget(const LayerType* new_target);
// Add the layer's occlusion to the tracked state.
void MarkOccludedBehindLayer(const LayerType* layer);
gfx::Rect screen_space_clip_rect_;
gfx::Size minimum_tracking_size_;
// This is used for visualizing the occlusion tracking process.
std::vector<gfx::Rect>* occluding_screen_space_rects_;
std::vector<gfx::Rect>* non_occluding_screen_space_rects_;
DISALLOW_COPY_AND_ASSIGN(OcclusionTracker);
};
#if !defined(COMPILER_MSVC)
extern template class OcclusionTracker<Layer>;
extern template class OcclusionTracker<LayerImpl>;
#endif
} // namespace cc
#endif // CC_TREES_OCCLUSION_TRACKER_H_